Ground supported structures or apparatus are susceptible to various forms of loading, including seismic and environmental load inputs, among others, over their useful life. One example of a supported structure is a circuit breaker for use in an electrical power grid assembly, shown in FIG. 1. This structure 10 is defined by a vertical mast 14 that supports an upper horizontally disposed cross member 18, the latter being configured for connection to a plurality of high tension lines 17. The length of the vertical mast 14 is considerably longer than that of the horizontal member 18, the latter being supported at the top of the vertical member 14 and therefore producing a high center of gravity (CG) that can also be eccentrically disposed in relation to the lower or bottom end of the structure 10 at which the structure is supported. The herein described structure 10 further includes a plurality of ceramic insulator disc-like plates 22 that are disposed in a sequential or stacked configuration axially along at least portions of each of the vertical mast 14 and horizontal cross member 18. When subjected to seismic loads, these ceramic insulator plates 22 may become more susceptible to cracking and fracture, which adversely affects performance. The time taken to inspect these structures for damage following a seismic event and the additional cost and time impact required for repair and replacement can be significant.
Therefore, it is generally accepted that such structures be decoupled from seismic loads, in an effort to isolate the structures and render them earthquake proof. Certain assemblies are known that provide isolation using wire rope isolators from compressive, tensile and shear loads. While such assemblies are highly effective for a number of supported structures, the high-CG and/or eccentric nature of structures such as depicted in FIG. 1 create multi-directional load inputs that cannot easily be compensated using only wire rope isolators.
As a result, it is a general desire to provide a reliably consistent seismic isolation assembly that improves the useful life and reliability of eccentrically constructed structures.